The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An internal combustion engine combusts mixed gas in which fuel and air are mixed at a predetermined ratio through a set ignition mode to generate power by using explosion pressure.
Generally, a camshaft is driven by a timing belt connected with a crankshaft that converts linear motion of a cylinder by the explosion pressure into rotating motion to actuate an intake valve and an exhaust valve, and while the intake valve is opened, air is suctioned into a combustion chamber, and while an exhaust valve is opened, gas which is combusted in the combustion chamber is exhausted.
To improve the operations of the intake valve and the exhaust valve and thereby improve engine performance, a valve lift and a valve opening/closing time (timing) are controlled according to a rotational speed of an engine. Therefore, a continuous variable valve duration (CVVD) device controlling the opening duration of an intake valve and an exhaust valve of the engine and a continuous variable valve timing (CVVT) device controlling the opening and closing timing of the intake valve and the exhaust valve of the engine have been developed.
The CVVD device adjusts duration of the valve by controlling an open time of the valve. In addition, the CVVT device advances or delays opening and closing timing of the valve in a state of fixing the open time of the valve. That is, if the opening timing of the valve is determined, the closing timing is automatically determined according to the open duration of the valve.
However, since both the CVVD device and the CVVT device are used in the engine, the duration and timing of the valve should be simultaneously controlled.